1. Field of the Invention
The present invention relates generally to failure or rupture detection mechanisms and, in one particular embodiment, to a rupture detector for a windshield assembly.
2. Technical Considerations
Windshield assemblies are used in various transportation-related fields for providing a vehicle operator with a clear view of the intended path of travel, while preventing environmental, physical and other impacts and/or interactions. For example, windshield assemblies are used in cars, trucks, buses, trains, aircraft, etc. These windshield assemblies must meet specific design requirements and specifications since a failure of the windshield could cause immediate harm and injury to the vehicle operator, vehicle passengers and others around the vehicle.
Vehicle transparencies, such as windshield assemblies, for high-speed transportation operations, such as aircraft or high-speed transit systems, require higher structural and safety measures due to the high speeds attained in these modes of transportation. Therefore, aircraft and high-speed transit system windshield assemblies are typically laminated assemblies having multiple interlayer material plies interposed between transparent rigid plies. These rigid plies can be glass or any other well-known substitutes, such as polycarbonates, acrylic resins, polyesters, and rigid transparent polyurethanes. This laminated structure provides the windshield with strength and flexibility.
In high-speed transportation operations, a failure of the vehicle transparency, e.g., windshield assembly, is particularly harmful not only to the operator but to the multiple passengers traveling within the vehicle. In the case of aircraft, a failure of the windshield assembly could cause depressurization of the cabin, force immediate landing (regardless of location) or could lead to the injury of both the operators and the passengers.
Due to the hazards presented by a failure or rupture in a vehicle transparency, e.g., windshield assembly, in these high-speed applications, the early detection of the onset of such a failure is particularly desirable. If a failure or rupture of a windshield assembly is detected early enough, the vehicle can be brought to a safe condition in a quicker manner or, alternatively, this early detection allows for early mitigation, thus increasing vehicle safety.
2b. Patents of Interest
U.S. Pat. No. 6,346,314 to Chaumel et al. teaches a device for locating a rupture in a transparent panel having multiple panes using an opaque or semi-opaque obstacle. This obstacle provides the vehicle operator with a visual indication of a windshield failure or break and further allows the operator to identify which pane has ruptured.
U.S. Pat. No. 4,994,650 to Koontz teaches an electric field detector for a heatable windshield and includes detector lines extending around a perimeter of the windshield. These detector lines are electrically interconnected to the windshield coating. As current passes through a coating on the windshield, voltage in the coating is monitored and interrupted in response to certain variations, for example a bus bar power lead failure.
U.S. Pat. No. 4,902,875 to Koontz teaches a power discontinuity sensor for a dual feed heatable windshield with bus bars having a double lead arrangement. Sensor lines extend adjacent the leads and are provided with current. Voltage in the lines is monitored and current to the bus bar is interrupted in response to certain variations.
It is, therefore, an object of the present invention to provide a rupture detector for a vehicle transparency, e.g., a windshield assembly, to detect a break or rupture in a layer of the windshield assembly, such as resulting from environmental or physical impact. It is another object of the present invention to provide a rupture detector that detects a break or rupture individually for multiple layers in a windshield assembly or different portions of a specific ply. It is yet another object of the present invention to provide a rupture detector for a windshield assembly that can be used in connection with any conventional windshield assembly, for example a xe2x80x9cplug-inxe2x80x9d or clamp-type windshield assemblies in an aircraft application
The present invention provides a rupture detector for detecting a rupture of a vehicle transparency, e.g., a windshield assembly, having one or multiple plies, e.g., transparent members. The rupture detector includes an electrically conductive member or strip attached to at least a portion of each or any individual transparent member. An electrical power source is in communication with the conductive member and applies an electrical potential to the conductive member. An electrical measurement mechanism, also in communication with the conductive member, measures the electrical potential of the conductive member. In one embodiment, the electrical power source is capable of applying known or predetermined current or voltage to the conductive member, and the electrical measurement mechanism is capable of reading the current or voltage and calculating the resistance. During a rupture or failure condition, as a crack or break passes into or through the conductive member, the resistance approaches and, when totally separated, reaches infinity, thereby indicating that a rupture has occurred. In one embodiment, the conductive member is a conductive band or coating extending around at least a portion of an outer periphery of the transparent member.
The present invention is also directed to a vehicle transparency, e.g., a windshield assembly, including one or multiple transparent members and a rupture detector. The rupture detector includes a conductive member or strip attached to at least a portion of each or any individual transparent member. An electrical power source is in communication with the conductive member and applies an electrical potential to the conductive member. An electrical measurement mechanism, also in communication with the conductive member, measures the electrical potential of the conductive member. The present invention is also directed to a method of detecting a rupture condition in a transparent member of a windshield assembly.
The present invention, both as to its construction and its method of operation, together with the additional objects and advantages thereof, will best be understood from the following description of exemplary embodiments when read in connection with the accompanying drawings.